Preparing for 6G: A Transceiver for Sub-THz frequencies
New transceivers able to handle transmission and reception at frequencies over 100 GHz and at 112 Gb/s data rate could pave the way to 6G technologies, according to scientists at Tokyo Tech. The proposed architecture reaches unprecedented data rates and is still a compact size by suppressing the self-interference caused by the transmission signal leaking into the receiver.
6G should deliver data rates of over 100 gigabits per second (Gb/s) and support extremely low latencies for applications such as autonomous cars and virtual reality. Adopting a full-duplex (FD) architecture operating at sub-THz frequencies from 88 to 136 GHz is possible. This architecture enables a single system to transmit and receive signals, doubling throughput. Implementation could occur by having transmission and reception modules share a single antenna, reducing the size of the circuit and allowing both parts to use the available frequency spectrum fully.
Single-antenna FD architectures suffer greatly from self-interference (SI), whereby the transmitted signal leaks into the receiver side. These systems must include circuits for SI cancellation to cancel the generated SI by injecting an equal signal with the opposite polarity. Implementing effective SI cancellation is much more challenging than in lower frequencies, which remains a hurdle to single-antenna FD designs.
Researchers from the Tokyo Institute of Technology developed a novel FD communication system addressing obstacles posed by SI. A prominent feature of the system is the implementation of a dual-polarized patch antenna. By making the circuit paths of these ports highly symmetrical, the mismatch of the transmitted signal that leaks into the differential receiver’s ports is minimized, keeping SI low. “
Another critical aspect of the proposed design is the SI cancellation (SIC) circuit. To effectively cancel the generated SI, one needs to carefully modify the phase of the cancellation signal so that it is opposite to that of the leaked signal. The researchers developed a new varactor structure that achieved excellent linear resolution over the entire sub-THz band and over the full 360° range.
